I have a 78 F250 400 and I have been kicking around the idea to get the engine machined. I have also been wondering if I should go with a 302 instead of the 400 to help with gas. Now I can't decide so maybe some of you can throw out some pros/cons for me since I am not familiar with either engine to help me figure out what will work for my situation.

I plan to use this truck a long long time if I can. It will be a daily driver and will be used for work as needed, like carrying stuff in the bed or maybe pulling a trailer or whatever it could be used for. Would a 302 work good in a F250 3/4 Ton truck? Will there be alot of headach swapping from a 400 to 302? Will I still be able to fit headers on it? There are a couple of the questions that keep coming to mind. I know a guy that has access to a bunch of 302 that he can get for pretty cheap OR maybe free. If I were to go that route I would just save up and have it machined since it is already out. Machineing it will let me know that it is a good working engine like new.

I will get the 400 machined if I keep it but I wonder if I have more engine than is needed for my use. Trying to save myself gas money and such in the long run.

Thanks
Larry

 

If I was totally worry about gas; I would replace your 400 with a 300 inline six; IMHO; I beleive a 3/4 ton needs a larger engine like your 400 to tackle heavy payloads. I also beleive all 250 etc; gas mileage is not an option. I personnelly think you won't see a tremendous difference in the 302 verse 400 on gas; but in preformance, will be biggest change. Also rear axle ratio is a large factor, in mileage as well.
Just my two cents worth, others are more knowledgeable and will debate my comments.

Mitch

 

In my opinion, The 302 was one the best auto engines ever made but it is marginal in a f250. The torque is not in the right rpms to pull heavy loads for long periods of time. I owned a 92 f150 4x4 with 302, it was great running empty on the Interstate but with a load, it was always on the floor just to pull a slight hill and would lose speed rapidly backing up traffic. I also don't think you will see much of a mileage improvements. The 302 will not bolt up, you must make lots of changes like bell housings, motor mounts etc. Unless you have a donor truck with all the 302 pieces I think it will be expensive to change over. The 400 was designed for trucks with a strong low-end torque curve for pulling. I admit 400s, they do use lots of gas but my 302 4x4 truck empty only got around 15 mpg at best. Loaded about 10mpg. I hope this helps!!!!!! Bart

 

Not sure on 4x4s... but with my 2wd, mileage stayed pretty much the same from a 302 to a 351W to a 460.

 

I agree, I have a 302 and is low on torque as mentioned above.

Machine the 400, it will have some good towing power,
maybe include a good RV Cam and the right sized Hypereutectic pistons for good quenching .

 

Thanks, this is what I needed to know. Since there really won't be much change in gas mileage and a very big project to to swap I will leave it alone and machine it.